Mortality for male unskilled and semi-skilled workers in Denmark, Norway, and England and Wales is 40-50%--about the average for all men with equivalent economic status in the younger age groups, but declines towards the average at pensionable age. The negative slope of the graph for relative mortality with age would seem to be due to an excess mortality deriving from accidents and violent deaths predominantly in the younger age groups, to an unfavourable recruitment into the labour force, health-wise, to an exclusion of older, unhealthy persons from the labour force and to a mortality from circulatory diseases almost equal to the average for other social groups. Finally, movements between social groups should be taken into account in the analysis of mortality differences.